The present invention relates to a system and associated method of operation for connecting a cellular communications network to a wide area network using a wireless connection.
More particularly, the present invention relates to a system and associated method of operation providing wireless connection from a cellular network to a wide area backbone network, wherein no additional independent or dedicated equipment is required, and the connection may be provided using existing network equipment used for normal data communications within the cellular network.
The reader is hereby referred to co-pending applications U.S. Appln. Ser. No. 09/540,995, entitled xe2x80x9cData Communications Method and Data Signalxe2x80x9d filed Mar. 30, 2000, and U.S. Appln. Ser. No. 09/548,183, entitled xe2x80x9cA Method and System for Data Traffic Schedulingxe2x80x9d filed Apr. 13, 2000, which are hereby incorporated herein by reference.
Within a cellular network the traffic in each cell must be aggregated at a central point into a single network medium for connection onto a wide area backbone or trunk network. Such a connection would typically be provided using a wired connection such as a coax or optical fibre line, known as the backhaul path. The backhaul path for each cell must have as much total bandwidth as the whole network in each cell, plus some overhead for network control and network management signalling.
In addition to using a wired connection, it is also known to instead pass the backhaul data via a wireless channel, provided that channel has sufficient bandwidth. The major advantage of using a wireless backhaul channel is that a cellular network deployment can be achieved without paying the substantial costs of providing wired backhaul to the central node at each cell site. Prior art implementations of wireless backhaul have, however, typically required additional network equipment to provide the wireless link, in that at least one dedicated backhaul terminal has typically been provided to which cell sites transmit their backhaul data for transmission onto the wide area network (WAN) via a standard wired connection, the backhaul terminal typically being of a different design to the normal customer subscriber terminals, and unable to operate as anything other than a backhaul terminal.
The present invention improves upon the known prior art by providing a method and system to provide a wireless backhaul connection from a cellular network to a wide area network in which at least one subscriber terminal in at least one of the network cells is able to act as the backhaul terminal, meaning that no additional network equipment is required to provide the backhaul connection.
According to the present invention, there is provided a method of wireless connection of a cellular communications network comprising one or more cells, each cell having a central control node and one or more remote subscriber nodes, to a wide area network, comprising the steps of:
connecting at least one remote subscriber node to the wide area network via a wired connection;
collecting backhaul data traffic to be transmitted to the wide area network from each network cell at the respective central control node in each cell; and
transmitting the backhaul data traffic from each central control node to the at least one remote subscriber node at least partway over a wireless backhaul channel.
Furthermore, according to the present invention, there is also provided a system providing wireless connection of a cellular communications network comprising one or more cells, each cell having a central control node and one or more remote subscriber nodes, to a wide area network, comprising:
a wired connection means for connecting at least one remote subscriber node to the wide area network;
means for collecting backhaul data traffic to be transmitted to the wide area network from each respective network cell, said means provided at the respective central control node of each cell; and
means for transmitting the backhaul data traffic from each central control node to the at least one remote subscriber node at least partway over a wireless backhaul channel.
The wireless channel to the subscriber terminal providing the is backhaul connection may be of an operating frequency and bandwidth that is well outside the normal operating band of the cellular network, or may instead be within the same band. In the latter case, highly directional antennas are used on the link to minimise co-channel interference with communications on the cellular network. The latter arrangement has the added advantage that spectral efficiency of the network is improved.
Preferably multiple backhaul connections provided for the cellular network, and in particular at least one backhaul connection is preferably provided for each network cell.
The subscriber terminals providing the backhaul connections may be located within the particular respective cells for which they are providing backhaul, or may be located outside the cells. In the case of the latter, the wireless link may be provided by an out-of-band microwave radio link, or a directional in-band radio link, and furthermore the subscriber terminal providing backhaul preferably does not also act as a customer terminal in that it provides network service to a customer.
Alternatively, in either case the connection between the central node of a particular cell to the subscriber terminal providing backhaul may be controlled within the same network layers as other network communications within the cell. That is, the wireless backhaul connection is provided as part of the network medium access control mechanism for controlling access of the subscriber nodes and of the central control node to the network medium in each cell. In the case where the medium access control mechanism is based upon a time division multiple access (TDMA) system, the backhaul data must be assigned time slots in which they may be transmitted to the subscriber terminal providing the backhaul connection. This has the disadvantage that the effective bandwidth available to the subscriber terminals in the cell in some cases is reduced by half, but has the advantage that the backhaul bandwidth may be dynamically assigned by the medium access controller as required. A further advantage is that greater flexibility and control may be achieved by integrating the backhaul connection into the network medium access control mechanism, and particularly during periods of high network loading.
It is an advantage of the present invention that because the backhaul connection is provided wirelessly, a solar powered base station can be deployed remotely without any land line power or backhaul